题目内容：
Which of the following best states the main idea of the final paragraph? A．Because doctors do not agree that flossing wilt help your heart, it is useless to floss．
B．It is a fact that flossing can help your heart as well as your teeth．
C．Even if flossing is only good for your teeth, you should still do it every day．
D．There is no good reason to believe that flossing will help your heart, but it is still a good idea to do it every day.
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